This invention relates to plastic drums for storing or transporting liquid and solid products. More specifically, the invention is directed to plastic drums having bottom-to-lid interlocking surfaces, which enable the drums to be placed in stacks that are both safe and stable during shipping or storing operations.
Plastic drums are commonly used in industry, particularly in chemical plants, to transport hazardous liquid and solid materials to disposal points, such as incinerators. Many of these drums have removable flat lids that are fastened to the drum with a ring clamp. When the drums are packed together inside a truck trailer, or on a pallet, the ring clamps are frequently damaged or dislodged from a drum. It's also quite difficult to use fork lift or parrotbeak equipment to move plastic drums that are filled with material. Lifting the drums with this type of equipment frequently loosens the ring clamp enough so that the lid drops off of the drum.
Another problem with plastic drums is the difficulty in trying to stack them to save space. When the drums are stacked, the flat bottom of the drum on top tends to slide on the flat lid of the drum on the bottom, so that the stack itself is very unstable. The flat lid can also collect water, or other liquids, which can be mistaken for hazardous waste materials.